1 /* ir-nec-decoder.c - handle NEC IR Pulse/Space protocol
3 * Copyright (C) 2010 by Mauro Carvalho Chehab
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation version 2 of the License.
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
15 #include <linux/bitrev.h>
16 #include <linux/module.h>
17 #include "rc-core-priv.h"
20 #define NEC_UNIT 562500 /* ns */
21 #define NEC_HEADER_PULSE (16 * NEC_UNIT)
22 #define NECX_HEADER_PULSE (8 * NEC_UNIT) /* Less common NEC variant */
23 #define NEC_HEADER_SPACE (8 * NEC_UNIT)
24 #define NEC_REPEAT_SPACE (4 * NEC_UNIT)
25 #define NEC_BIT_PULSE (1 * NEC_UNIT)
26 #define NEC_BIT_0_SPACE (1 * NEC_UNIT)
27 #define NEC_BIT_1_SPACE (3 * NEC_UNIT)
28 #define NEC_TRAILER_PULSE (1 * NEC_UNIT)
29 #define NEC_TRAILER_SPACE (10 * NEC_UNIT) /* even longer in reality */
30 #define NECX_REPEAT_BITS 1
42 * ir_nec_decode() - Decode one NEC pulse or space
43 * @dev: the struct rc_dev descriptor of the device
44 * @duration: the struct ir_raw_event descriptor of the pulse/space
46 * This function returns -EINVAL if the pulse violates the state machine
48 static int ir_nec_decode(struct rc_dev
*dev
, struct ir_raw_event ev
)
50 struct nec_dec
*data
= &dev
->raw
->nec
;
52 u8 address
, not_address
, command
, not_command
;
53 bool send_32bits
= false;
55 if (!is_timing_event(ev
)) {
57 data
->state
= STATE_INACTIVE
;
61 IR_dprintk(2, "NEC decode started at state %d (%uus %s)\n",
62 data
->state
, TO_US(ev
.duration
), TO_STR(ev
.pulse
));
64 switch (data
->state
) {
70 if (eq_margin(ev
.duration
, NEC_HEADER_PULSE
, NEC_UNIT
* 2)) {
71 data
->is_nec_x
= false;
72 data
->necx_repeat
= false;
73 } else if (eq_margin(ev
.duration
, NECX_HEADER_PULSE
, NEC_UNIT
/ 2))
74 data
->is_nec_x
= true;
79 data
->state
= STATE_HEADER_SPACE
;
82 case STATE_HEADER_SPACE
:
86 if (eq_margin(ev
.duration
, NEC_HEADER_SPACE
, NEC_UNIT
)) {
87 data
->state
= STATE_BIT_PULSE
;
89 } else if (eq_margin(ev
.duration
, NEC_REPEAT_SPACE
, NEC_UNIT
/ 2)) {
90 if (!dev
->keypressed
) {
91 IR_dprintk(1, "Discarding last key repeat: event after key up\n");
94 IR_dprintk(1, "Repeat last key\n");
95 data
->state
= STATE_TRAILER_PULSE
;
102 case STATE_BIT_PULSE
:
106 if (!eq_margin(ev
.duration
, NEC_BIT_PULSE
, NEC_UNIT
/ 2))
109 data
->state
= STATE_BIT_SPACE
;
112 case STATE_BIT_SPACE
:
116 if (data
->necx_repeat
&& data
->count
== NECX_REPEAT_BITS
&&
117 geq_margin(ev
.duration
,
118 NEC_TRAILER_SPACE
, NEC_UNIT
/ 2)) {
119 IR_dprintk(1, "Repeat last key\n");
121 data
->state
= STATE_INACTIVE
;
124 } else if (data
->count
> NECX_REPEAT_BITS
)
125 data
->necx_repeat
= false;
128 if (eq_margin(ev
.duration
, NEC_BIT_1_SPACE
, NEC_UNIT
/ 2))
130 else if (!eq_margin(ev
.duration
, NEC_BIT_0_SPACE
, NEC_UNIT
/ 2))
134 if (data
->count
== NEC_NBITS
)
135 data
->state
= STATE_TRAILER_PULSE
;
137 data
->state
= STATE_BIT_PULSE
;
141 case STATE_TRAILER_PULSE
:
145 if (!eq_margin(ev
.duration
, NEC_TRAILER_PULSE
, NEC_UNIT
/ 2))
148 data
->state
= STATE_TRAILER_SPACE
;
151 case STATE_TRAILER_SPACE
:
155 if (!geq_margin(ev
.duration
, NEC_TRAILER_SPACE
, NEC_UNIT
/ 2))
158 address
= bitrev8((data
->bits
>> 24) & 0xff);
159 not_address
= bitrev8((data
->bits
>> 16) & 0xff);
160 command
= bitrev8((data
->bits
>> 8) & 0xff);
161 not_command
= bitrev8((data
->bits
>> 0) & 0xff);
163 if ((command
^ not_command
) != 0xff) {
164 IR_dprintk(1, "NEC checksum error: received 0x%08x\n",
170 /* NEC transport, but modified protocol, used by at
171 * least Apple and TiVo remotes */
172 scancode
= data
->bits
;
173 IR_dprintk(1, "NEC (modified) scancode 0x%08x\n", scancode
);
174 } else if ((address
^ not_address
) != 0xff) {
176 scancode
= address
<< 16 |
179 IR_dprintk(1, "NEC (Ext) scancode 0x%06x\n", scancode
);
182 scancode
= address
<< 8 | command
;
183 IR_dprintk(1, "NEC scancode 0x%04x\n", scancode
);
187 data
->necx_repeat
= true;
189 rc_keydown(dev
, RC_TYPE_NEC
, scancode
, 0);
190 data
->state
= STATE_INACTIVE
;
194 IR_dprintk(1, "NEC decode failed at count %d state %d (%uus %s)\n",
195 data
->count
, data
->state
, TO_US(ev
.duration
), TO_STR(ev
.pulse
));
196 data
->state
= STATE_INACTIVE
;
200 static struct ir_raw_handler nec_handler
= {
201 .protocols
= RC_BIT_NEC
,
202 .decode
= ir_nec_decode
,
205 static int __init
ir_nec_decode_init(void)
207 ir_raw_handler_register(&nec_handler
);
209 printk(KERN_INFO
"IR NEC protocol handler initialized\n");
213 static void __exit
ir_nec_decode_exit(void)
215 ir_raw_handler_unregister(&nec_handler
);
218 module_init(ir_nec_decode_init
);
219 module_exit(ir_nec_decode_exit
);
221 MODULE_LICENSE("GPL");
222 MODULE_AUTHOR("Mauro Carvalho Chehab");
223 MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
224 MODULE_DESCRIPTION("NEC IR protocol decoder");